Advances in prevention science have identified risk and protective factors that predict health outcomes including substance abuse as well as efficacious preventive interventions. Yet, translating prevention science into community prevention service systems has been difficult and has emerged as a priority for prevention services research (Backer, 2000; Biglan, 1995). The proposed project is a randomized controlled trial of the Communities That Care (CTC) prevention operating system. CTC provides a framework for risk and protective focused prevention as well as training, technical assistance, and tools to guide community assessment, planning and action to implement and institutionalize science-based prevention services systems (Hawkins, Catalano & Associates, 1992; Developmental Research and Programs, 1997, 2000). The study is a joint effort of the Social Development Research Group of the University of Washington, the State Substance Abuse Prevention Agencies of Colorado, Illinois, Kansas, Maine, Oregon, Utah, and Washington, and 24 communities in these states. The five-year experimental study seeks to test the effects of the CTC operating system on levels and trends in risk, protection, drug use, violence and antisocial behavior among adolescents in grades 6 through 12 and on prevention services in communities including levels of collaboration, use of epidemiologic data on risk and protection to guide prevention planning, and adoption and implementation of tested effective preventive interventions. Building on a current five-year study of prevention services in these 24 communities, the proposed study will randomly assign one community from each of 12 community pairs to receive the CTC intervention, while the other will serve as a control. Intervention communities will receive training, technical assistance and materials needed to install the CTC operating system, a community coordinator, and funding in years 2-5 to implement tested preventive interventions needed to fill prevention service gaps. Measures of coordination/collaboration, implementation of risk and protection focused prevention planning, and evidence-based prevention services will be collected in all communities. The impact of CTC on youth outcomes will be assessed by extending existing trend data on risk and protective factors and adolescent problem behaviors in participating communities through surveys of 6th, 8th, 10th, and 12th grade students administered in years 2, 4, and 5 of the proposed study, and by annual surveys of a representative panel of 4th grade students in each community constituted in the first year of the study.